Can I visit the Bangkok immigration office after my visa expires without incurring an overstay fine?

If your non-exempt visa expires on a day when the immigration office is closed (like a weekend), you can visit the office the following business day without facing an overstay fine. You will receive a stamp indicating overstay, but it will state that the fine is waived. It's important to note that you don't need to wait until your visa is about to expire to apply for an extension, as new validity will be added to the existing expiration date.